Low salivary thioredoxin-1 levels in periodontitis

The protein thioredoxin-1 (TRX-1) has anti-oxidative, anti-inflammatory and anti-apoptotic effects, and it has been related to the regulation of ageing and different diseases. TRX-1 in periodontitis has been scarcely studied, and the results in humans and in mice are contradictory. In three small studies with humans (the highest with 96 subjects), it was found that patients with periodontitis, compared to periodontally healthy subjects, showed a higher expression of TRX-1 or of the TRX-1 gene in saliva. However, in one study with mice, it was found that mice with periodontitis, compared to periodontally healthy mice, showed a lower expression of TRX-1 in the periodontal tissues.

To explore the possible association of salivary TRX-1 concentrations with periodontitis and its severity, and of determining the capability of salivary TRX-1 concentrations to predict the diagnosis of periodontitis in a larger sample size study.

Salivary TRX-1 concentrations were measured in subjects with and without periodontitis in this observational and prospective study. Criteria to establish periodontal health were the nonexistence, or existence in less than 10% of sites, of bleeding on probing, and the nonexistence of interproximal attachment and bone loss. Criteria to establish localized gingivitis were the existence of bleeding between 10%-30% of sites, and the nonexistence of interproximal attachment and bone loss. Criteria to establish periodontitis were the existence of interproximal attachment or bone loss. We carried out a multivariate logistic regression analysis to determine the variables associated with periodontitis, a correlation analysis to determine the possible association between salivary TRX-1 concentrations and periodontitis severity, and a receiver operating characteristic (ROC) analysis to determine the capability of salivary TRX-1 concentrations to predict the diagnosis of periodontitis.

A total of 144 subjects (58 with periodontitis and 86 without periodontitis) were included. Low salivary TRX-1 concentrations showed an association with periodontitis (P = 0.04) according to regression analysis, an association with periodontitis severity (rho = -0.47; P < 0.001) according to correlation analysis, and an area under curve of 75% (95%CI: 67%-82%; P < 0.001) for periodontitis diagnosis according to ROC analysis.

Novel findings of this study were the association of low salivary TRX-1 concentrations with periodontitis and its severity, and the capacity of salivary TRX-1 concentrations to help in the periodontitis diagnosis.